We were hit with a ransomware attack back in 2019 and lost our Exchange Server 2016. We synced our users from Active Directory to 365 and gave them new mailboxes. Then, we reinstalled Exchange 2016 and restored our old mailboxes. We migrated users' messages from their old mailboxes on the restored-on-premise-server to their new 365 mailboxes. What does this give us? “Identity Hybrid”? The on-premise Exchange server is 2016 with CU19 installed on Windows 2016. It still has all the server roles and footprint as when it was a mailbox and transport server. I’m not confident in my AD setup as far as Exchange is concerned. I’d like to get that disk space back and clean up my environmCan ent. Can I remove the old unused mailboxes and the any link from the AD accounts to them? Can I remove the unused server roles from the server and from Active Directory. Can I migrate the 2016 server to a new server Exchange 2019 on Windows 2019 with only with only the hardware and functionality needed for “Identity Hybrid”? Or decomission the server and install a 2019 server on-premise for management?
Sorry if I got the tags wrong, or composed the descripton of this mess poorly